The most well-known Indonesian instruments is arguably the gamelan, a term that refers to an full music ensemble rather than an instrument. Wikipedia has a good article on it.
The gamelan is originally from the islands of Java and Bali, but it is widely used (even though usually not all the instruments together) throughout Indonesia.
Full gamelan sets can be seen in the palace of the sultan of Solo or Yogyakarta. The museum in Yogyakarta facing the palace also have some on displays.
The Sundanese of West Java have use a customized gamelan called gamelan degung that they use to make a very peaceful traditional music called Degung Sunda.
This style of music is easily associated to Bali (who also use gamelan in traditional music) while this is pure Sundanese culture. The use of the flute (seruling) is very characteristic. You can find many albums of that music style on Youtube.
West Java and Banten have also given the angklung to Indonesia. Children are very often taught to play it at school.
Another very cool music style I discovered through the awesome website Aural Archipelago is Daul from Madura :
A couple of more modern songs
Iwan Falls was very popular in the 90s and is still a favorite of many. His songs are quite political, tackling issues like war (Puing), environment (Isi Rimba Tak Ada Tempat Berpijak Lagi) or poverty (Siang Sebrang Istana)
In the early 2000s, I feel that the biggest thing was the band Peterpan from Bandung and its lead singer Ariel. Ariel was latter embroiled in a scandal case of sextapes which sent him to jail for some time. The band eventually came back under the name Noah.
A huge recent hit, you can hear it all the time during the Ramadhan month :
A few more songs, both old and new :
Music in everyday life
Indonesia is a nation of great musicians. I was often impressed by the fact that so many people seem to own a musical talent, either singing or playing an instrument.
Street musicians, called pengamen, very often hop on buses or stroll between the table of street restaurants to get a bit of money. Some of them can be very talented, like this girl who had latter been invited on TV (the original song is Kristina – Secawan Madu) :
People often given between 500 and 2’000Rp, from 5’000 you’re being generous by Indonesian standards.
When the driver is not into cheap pop music, bus rides can be a great way to discover regional music, sang in the local language. The first following song is in Sundanese, the second one in Batak Toba :
Dangdut and Indonesian pop music
Dangdut is a rather bizarre genre that is almost a synonym for traditional Indonesian pop music. For an external ear, sometimes you may believe that you are listening to some Indian or Arabic music.
80% of the Indonesian songs in general are love songs, I would say it’s ever more than that in the case of dangdut with has usually very shallow lyrics. Add to that a taste for cheap synthetic tunes and a passion shared by many to blast music at full volume with a disproportionate level of bass and you have something quite “particular”.
If many Indonesian are into dangdut, many also confess their preference for something else. Still, many of the major hits until today are at least dangdut inspired : Lagi Syantik by Siti Badriah, Goyang 2 Jari by Sandrina, Sambalado by Ayu Ting Ting, Kereta Malam or Buka Dikit Joss by Juwita Bahar…
To me, dangdut is often painful to hear, yet from times to times it can be touching, like this cover of Ampunilah by Rhoma Iroma (‘the Dangdut King’) on TV :
Fortunately, Indonesia does also make some more classic pop music :